The present invention relates to lamp lighting circuits, and more particularly to a circuit which indicates a failure of a lamp within a lighting system where the lamps are connected in series.
Environments exist where it is desirable to implement lamps wired in series. Such situations may include having a low voltage lamp which provides better performance than a higher voltage equivalent lamp, or when a higher voltage lamp is not practical or feasible due to wire size limitations or for other parameter requirements. For example, in the United States the standardized input power line is 120-volt a.c. However, a high-efficiency quartz halogen lamp has not be designed for efficient operation at the 120-volt a.c. input line. Rather, quartz halogen lamps operate most efficiently with a low-voltage coil or filament, in order to obtain a high lumen-per-watt efficiency output. Therefore, to operate a low-voltage lamp (e.g. a 40-watt quartz halogen lamp) it is necessary to provide a ballast for each lamp to limit the 120-volt a.c. input to an appropriate lamp operating voltage. However, ballasts are at times bulky and add economic cost to lamp lighting systems.
A manner in which low-voltage lamps may be operated without the implementation of a ballast is by placing the lamps in series. For example, if 120-volt a.c. input line is considered as being standard, placing three 40-volt lamps in series allows each lamp to operate at its normal rated voltage.
A significant obstacle to wiring lamps in series however, is that when a lamp in the series fails, the entire circuit is broken and all lamps in the series are deactivated. In this situation, replacing the failed lamp requires a pick-and-choose solution, where lamps are randomly replaced to determine whether a selected lamp has failed. This requires the lamp system to be deactivated. Next, a lamp is randomly selected and removed from the system, a new lamp is inserted to replace the removed lamp, and the lighting system is supplied with power. If the replaced lamp is not the failed lamp, the process is repeated until the failed lamp is found.
This process is tedious and inefficient and discourages the practice of placing lamps in a series arrangement, even when such a configuration would be otherwise beneficial.
Therefore, it has been considered desirable by the inventors to develop a mechanism which provides a clear indication of which lamp in a series of lamps has failed, in order to provide an efficient manner of replacing the failed lamp.
A plurality of lamps are connected in series. A plurality of burnout detector mechanisms are provided where one of the burnout protection mechanisms from the plurality is connected across a corresponding lamp of the plurality of serially connected lamps. When a lamp in the series enters a failure state, the burnout detector mechanism is activated providing an indication as to the burned out lamp. Dependant upon the values provided in the burnout detector mechanism and the type of lamps, the non-failed lamps will either enter an OFF state, or a low-light glow state when a burnout detection mechanism is active.